A number of structures have been developed which are designed to float, for various purposes, on molten metals and alloys. For example, U.S. Pat. No. 3,633,666 to Sparks discloses a floating heat conductor on a molten metal in a metal furnace. The floating heat conductor of Sparks is made from silicon carbide.
U.S. Pat. No. 3,729,097 to Collins et al and U.S. Pat. No. 4,113,241 to Dore each disclose filter devices which are designed to be floated in a pool of molten metal. The filters of Collins et al and Dore are made from dense graphite.
U.S. Pat. No. 4,106,905 to Schmitt et al discloses floating a layer of hollow discrete particles on a molten bath. The layer of hollow particles provide an insulating cover. The hollow particles are made from various materials listed at column 3 of Schmitt et al.
The above patents represent some of the more common floating articles which are utilized in conjunction with molten materials. In addition to the above devices which provide for insulation, heat conduction, and support of filtering devices, a few floating structures have been specially developed more recently for use in aluminum reduction cells.
U.S. Pat. No. 4,533,452 to Leroy et al discloses a floating screen which includes either floating balls or a single structure or a plurality of interlocking plates. The floating screen elements are made from TiB.sub.2 coated porous structures which many have porous TiB.sub.2 or graphite cores, or cores made from a mixture of materials. In use, the floating screen is positioned between the anode and cathode, at the interface of the liquid aluminum sheet and the layer of electrolyte and is not connected to the cathode.
U.S. Pat. No. 4,532,017 to Keinborg et al discloses floating cathode elements which are utilized in Hall-Heroult cells for the production of aluminum. The floating cathode elements are made from composites which include floating substrates, such as graphite and TiB.sub.2 materials. The floating cathodes are secured by anchoring means.
The present invention in an improvement over prior art materials devices which are floatable on molten materials, particularly molten aluminum.